1. Field of the Invention
The present invention relates to an electrical connector, and more particularly to electrical connectors with improved contact arrangement.
2. Description of Related Art
Universal Serial Bus (USB) is used widely in various electronic devices as a standard and simple interface. Up to now, previous notable releases of the USB specification were 0.9, 1.0, 1.1 and 2.0. Equipment conforming to any version of the standard will also work with devices designed to any previous specification (known as: backward compatibility).
USB mentioned above supports three data rates respectively as follows: 1) A Low Speed rate of up to 1.5 Mbit/s (187.5 KB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks; 2) A Full Speed rate of up to 12 Mbit/s (1.5 MB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed; 3) A Hi-Speed rate of up to 480 Mbit/s (60 MB/s).
However, as the development of electric industry, even the USB 2.0 can not satisfy the requirement of many electric devices. For example, under a circumstance transmitting an audio or video file, which is always up to hundreds MB, even to 1 or 2 GB, currently transmission rate of USB is not sufficient. As a consequence, faster serial-bus interfaces are being introduced to address different requirements. PCI Express, at 2.5 GB/s, and SATA, at 1.5 GB/s and 3.0 GB/s, are two examples of High-Speed serial bus interfaces.
However, these non-USB protocols, such as PCI Express which is useful for its higher possible data rates, a 26-pin connectors and wider card-like form factor limit the use of Express Cards, and SATA which uses two connectors, one 7-pin connector for signals and another 15-pin connector for power, are not used as broadly as USB protocols. Many portable devices are equipped with USB connectors other than these non-USB connectors. One important reason is that these non-USB connectors contain a greater number of signal pins than an existing USB connector and are physically larger as well, and the greater number of signal pins is assembled difficultly, especially in an electrical connector. Due to its clumsiness, the PCI Express and SATA connector can not adapt to the development trend of gently, thin, short and small size.
USB connector is soldered on a circuit board of a computer usually. The USB 2.0 A type connector according to USB-IF usually comprises an insulative housing with a tongue plate extending forwardly, four contacts retained in the insulative housing and a metal shield. Each contact has a contact portion extending to a lower side of the tongue plate and exposing out thereof flexibly. The contact portion presents as arc type and can move along a thickness direction of the tongue. The four contacts comprise a power contact, a grounding contact, a − data contact and a + data contact. The − data contact and + data contact present as a pair of differential signal contacts which are located between the power contact and the grounding contact. The metal shield encloses the tongue plate and forms a first receiving space for receiving a USB plug.
Hence, an electrical connector which is based USB interface, but has a high signal transmission speed and an improved contacts arrangement, is desired to overcome the disadvantage of the prior art.